node:tls: implement setDefaultCACertificates()

packages/bun-usockets/src/crypto/openssl.c

@@ -139,7 +139,8 @@ static int us_sni_ex_idx = -1;
 static int us_ctx_cache_ex_idx = -1;
 /* Marks an SSL_CTX whose verification store holds user-provided CAs (the
  * ca/caFile options or a later addCACert): the per-socket client attach must
- * not replace such a store with the process-shared default roots. */
+ * not replace such a store with the process-shared default roots, and
+ * tls.setDefaultCACertificates() must not override it either. */
 static int us_ctx_user_ca_ex_idx = -1;
 static int us_ssl_reneg_state_idx = -1;
 /* Per-connection async-SNI suspension state (select_certificate_cb retry). */
@@ -1164,9 +1165,9 @@ void us_internal_ssl_attach(struct us_socket_t *s, SSL_CTX *ctx,
      * bundle without touching the CTX (servers using the same CTX never pay
      * the ~150-root build). us_verify_callback returns 1 so the handshake
      * never aborts here — JS reads verify_error and decides. */
+    us_ex_idx_ensure();
     if (SSL_CTX_get_verify_mode(ctx) == SSL_VERIFY_NONE) {
       SSL_set_verify(ssl, SSL_VERIFY_PEER, us_verify_callback);
-      us_ex_idx_ensure();
       if (!SSL_CTX_get_ex_data(ctx, us_ctx_user_ca_ex_idx)) {
         /* Default context: give this socket the process-shared root bundle.
          * A context whose store holds user-provided CAs (ca/caFile options or
@@ -1175,6 +1176,16 @@ void us_internal_ssl_attach(struct us_socket_t *s, SSL_CTX *ctx,
         X509_STORE *roots = us_get_shared_default_ca_store();
         if (roots) SSL_set0_verify_cert_store(ssl, roots);
       }
+    } else if (us_has_user_root_certs()
+               && !SSL_CTX_get_ex_data(ctx, us_ctx_user_ca_ex_idx)) {
+      /* CTX was built against the process defaults (request_cert without an
+       * explicit `ca`), but tls.setDefaultCACertificates() has since replaced
+       * those defaults. Override the verify store for this SSL only so the
+       * new roots take effect without rebuilding the cached SSL_CTX
+       * (fetch()/https.request() cache their HTTPS context for the process
+       * lifetime). CTXs with user CAs are left alone. */
+      X509_STORE *roots = us_get_shared_default_ca_store();
+      if (roots) SSL_set0_verify_cert_store(ssl, roots);
     }
   } else {
     SSL_set_accept_state(ssl);

packages/bun-usockets/src/crypto/root_certs.cpp

@@ -1,6 +1,7 @@
 #include "./root_certs.h"
 #include "./root_certs_header.h"
 #include "./internal/internal.h"
+#include <atomic>
 #include <mutex>
 #include <string.h>
 #include "./default_ciphers.h"
@@ -187,6 +188,67 @@
   return us_get_default_ca_certificates()->root_extra_cert_instances;
 }
 
+// ---------------------------------------------------------------------------
+// User-overridden default CA certificates (tls.setDefaultCACertificates)
+//
+// Node.js lets JS replace the default trust root set at runtime. Once set,
+// *every* consumer of the "default" store — us_get_default_ca_store() and
+// us_get_shared_default_ca_store() — must ignore the bundled/system/extra
+// sources and build the store purely from this user-supplied set. The
+// override is process-global here (Node.js uses thread_local so Workers are
+// isolated; we accept the simpler process-wide semantics for now) and guarded
+// by shared_store_mutex because the shared store can be read from socket
+// I/O paths on other threads while JS swaps it.
+// ---------------------------------------------------------------------------
+static std::mutex shared_store_mutex;
+static X509_STORE *shared_store = nullptr;
+static STACK_OF(X509) *user_root_certs = nullptr;
+// Atomic so the lock-free fast-path check in us_has_user_root_certs()
+// (called per-SSL from us_internal_ssl_attach) is well-defined when a
+// Worker is concurrently setting the override. Relaxed is enough: a
+// stale false falls through to the shared-store path (which also honours
+// the override under the mutex), a stale true just costs one extra
+// SSL_set0_verify_cert_store.
+static std::atomic<bool> has_user_root_certs { false };
+
+extern "C" int us_has_user_root_certs() {
+  return has_user_root_certs.load(std::memory_order_relaxed) ? 1 : 0;
+}
+
+extern "C" void us_set_user_root_certs(STACK_OF(X509) *certs) {
+  std::lock_guard<std::mutex> lock(shared_store_mutex);
+  if (user_root_certs) {
+    sk_X509_pop_free(user_root_certs, X509_free);
+  }
+  user_root_certs = certs; // may be nullptr for an explicit empty set
+  has_user_root_certs = true;
+
+  // Drop the cached shared store so the next consumer rebuilds from the
+  // override. Existing SSL*s already hold their own X509_STORE reference via
+  // SSL_set0_verify_cert_store, so this only affects new connections.
+  if (shared_store) {
+    X509_STORE_free(shared_store);
+    shared_store = nullptr;
+  }
+}
+
+STACK_OF(X509) *us_dup_user_root_certs(bool *out_has_override) {
+  // Hand back an owned, up-ref'd snapshot so the caller can serialise the
+  // certs to PEM without racing us_set_user_root_certs() on another Worker.
+  // *out_has_override distinguishes "no override installed" from "empty
+  // override installed" (both return nullptr). Caller frees the returned
+  // stack via sk_X509_pop_free(.., X509_free).
+  std::lock_guard<std::mutex> lock(shared_store_mutex);
+  if (out_has_override) *out_has_override = has_user_root_certs;
+  if (user_root_certs == nullptr) return nullptr;
+  STACK_OF(X509) *dup = sk_X509_dup(user_root_certs);
+  if (dup == nullptr) return nullptr;
+  for (size_t i = 0; i < sk_X509_num(dup); i++) {
+    X509_up_ref(sk_X509_value(dup, i));
+  }
+  return dup;
+}
+
 // Single source of truth for the OS trust store. Loaded on first demand,
 // independent of --use-system-ca / NODE_USE_SYSTEM_CA, so that
 // tls.getCACertificates('system') matches Node.js (which always reads the
@@ -207,12 +269,28 @@
   return system_certs;
 }
 
-extern "C" X509_STORE *us_get_default_ca_store() {
+static X509_STORE *us_build_default_ca_store_locked() {
   X509_STORE *store = X509_STORE_new();
   if (store == NULL) {
     return NULL;
   }
 
+  // If JS overrode the defaults via tls.setDefaultCACertificates(), honour
+  // that exclusively — Node.js does not merge bundled/system/extra back in.
+  // X509_STORE_add_cert() takes its own reference, so no up_ref here —
+  // unlike the bundled/extra/system blocks below (whose certs are
+  // process-lifetime statics so the extra ref is harmless), user_root_certs
+  // is freed on every subsequent setDefaultCACertificates() and an extra
+  // ref would leak.
+  if (has_user_root_certs) {
+    if (user_root_certs) {
+      for (int i = 0; i < (int)sk_X509_num(user_root_certs); i++) {
+        X509_STORE_add_cert(store, sk_X509_value(user_root_certs, i));
+      }
+    }
+    return store;
+  }
+
   if (!X509_STORE_set_default_paths(store)) {
     X509_STORE_free(store);
     return NULL;
@@ -253,18 +331,30 @@
   return store;
 }
 
-// Process-wide immutable default store. Safe to share across SSL_CTXs that
-// don't add per-config CAs (the user-`ca` path in build_raw populates the
-// SSL_CTX's own private, initially-empty store instead). This makes the
-// ~150-root build a once-per-process cost instead of once-per-SSL_CTX, which
-// is what kept Bun.connect({tls:true}) under the node-tls-server.test.ts
-// 100ms cold-path budget in debug+ASAN.
+extern "C" X509_STORE *us_get_default_ca_store() {
+  // Serialise with us_set_user_root_certs() so a Worker swapping the
+  // override can't race another Worker building a per-config store.
+  std::lock_guard<std::mutex> lock(shared_store_mutex);
+  return us_build_default_ca_store_locked();
+}
+
+// Process-wide default store cached behind a mutex. Safe to share across
+// SSL_CTXs that don't add per-config CAs (the user-`ca` path in build_raw
+// populates the SSL_CTX's own private, initially-empty store instead). This
+// makes the ~150-root build a once-per-process cost instead of
+// once-per-SSL_CTX, which is what kept Bun.connect({tls:true}) under the
+// node-tls-server.test.ts 100ms cold-path budget in debug+ASAN.
+//
+// Not std::call_once: tls.setDefaultCACertificates() must be able to
+// invalidate the cached store so subsequent connections see the override.
+// us_set_user_root_certs() takes the same mutex and nulls shared_store.
 extern "C" X509_STORE *us_get_shared_default_ca_store() {
-  static X509_STORE *shared = nullptr;
-  static std::once_flag once;
-  std::call_once(once, []() { shared = us_get_default_ca_store(); });
-  if (shared) X509_STORE_up_ref(shared);
-  return shared;
+  std::lock_guard<std::mutex> lock(shared_store_mutex);
+  if (shared_store == nullptr) {
+    shared_store = us_build_default_ca_store_locked();
+  }
+  if (shared_store) X509_STORE_up_ref(shared_store);
+  return shared_store;
 }
 
 extern "C" const char *us_get_default_ciphers() {

packages/bun-usockets/src/crypto/root_certs_header.h

@@ -6,10 +6,13 @@
 
 STACK_OF(X509) *us_get_root_extra_cert_instances();
 STACK_OF(X509) *us_get_root_system_cert_instances();
+STACK_OF(X509) *us_dup_user_root_certs(bool *out_has_override);
 
 #else
 #define CPPDECL extern
 #endif
 
 CPPDECL X509_STORE *us_get_default_ca_store();
 CPPDECL X509_STORE *us_get_shared_default_ca_store();
+CPPDECL void us_set_user_root_certs(STACK_OF(X509) *certs);
+CPPDECL int us_has_user_root_certs();